package com.yundasys.lab12java.lru;

import java.util.HashMap;
import java.util.Map;

/**
 * @author jiangta
 * @version 1.0
 * @date 2022/3/21 1:29 下午
 */
public class LRUCacheDemo {

    //map负责查找，构建一个虚拟的双向链表，它里面安装的就是一个个Node节点，作为数据载体

    //构造Node节点，作为数据载体
    class Node<K,V> {
        K key;
        V value;
        Node<K,V> prev;
        Node<K,V> next;

        public Node() {
            this.prev =this.next=null;
        }

        public Node(K key,V value) {
            this.key = key;
            this.value = value;
            this.prev = this.next = null;
        }
    }

    //构造一个双向队列
    class DoubleLinkedList<K,V> {
        Node<K,V> head;
        Node<K,V> tail;
        public DoubleLinkedList() {
            head = new Node<>();
            tail = new Node<>();
            head.next = tail;
            tail.prev = head;
        }

        public void addHead(Node<K,V> node) {
            node.next=head.next;
            node.prev=head;
            head.next.prev=node;
            head.next=node;
        }

        public void removeNode(Node<K,V> node) {
            node.prev.next = node.next;
            node.next.prev = node.prev;
            node.next = null;
            node.prev = null;
        }

        public Node getLast() {
            return tail.prev;
        }
    }

    private int cacheSize;
    Map<Integer,Node<Integer,Integer>> map;
    DoubleLinkedList<Integer,Integer> doubleLinkedList;

    public LRUCacheDemo(int cacheSize) {
        this.cacheSize = cacheSize;
        map = new HashMap<>();
        doubleLinkedList = new DoubleLinkedList<>();
    }

    public int get(int key) {
        if(!map.containsKey(key)) {
            return -1;
        }
        Node<Integer, Integer> node = map.get(key);
        doubleLinkedList.removeNode(node);
        doubleLinkedList.addHead(node);
        return node.value;
    }

    public void put(int key,int value) {
        if(map.containsKey(key)) {
            Node<Integer, Integer> node = map.get(key);
            node.value = value;
            map.put(key,node);

            doubleLinkedList.removeNode(node);
            doubleLinkedList.addHead(node);
        } else {
            if(map.size() == cacheSize){
                Node last = doubleLinkedList.getLast();
                map.remove(last.key);
                doubleLinkedList.removeNode(last);
            }
            Node newNode = new Node(key, value);
            map.put(key, newNode);
            doubleLinkedList.addHead(newNode);
        }
    }

    public static void main(String[] args) {
        LRUCacheDemo lruCacheDemo = new LRUCacheDemo(3);
        lruCacheDemo.put(1,1);
        lruCacheDemo.put(2,2);
        lruCacheDemo.put(3,3);
        System.out.println(lruCacheDemo.map.keySet());

        lruCacheDemo.put(4,1);
        System.out.println(lruCacheDemo.map.keySet());

        lruCacheDemo.put(3,1);
        System.out.println(lruCacheDemo.map.keySet());
        lruCacheDemo.put(3,1);
        System.out.println(lruCacheDemo.map.keySet());
        lruCacheDemo.put(3,1);
        System.out.println(lruCacheDemo.map.keySet());

        lruCacheDemo.put(5,1);
        System.out.println(lruCacheDemo.map.keySet());
    }
}
